Haemophilus ducreyi, the etiologic agent of the genital ulcer disease chancroid. H. ducreyi makes a major outer membrane protein (MOMP) that may stabilize the H. ducreyi outer membrane. The purpose of this study is to test the hypothesis that a MOMP deficient mutant of H. ducreyi is impaired in its ability to infect human skin when compared to its isogenic parent. To test this hypothesis, we will compare the ability of H. ducreyi strain 35000HP and its isogenic MOMP mutant to cause experimental infection in human subjects in dose response studies. These studies will directly test whether MOMP plays a role in the ability of H. ducreyi to cause skin ulcer.